Initial commit

go.mod

@@ -0,0 +1,6 @@
+module code.bluelife.at/decke/smtp-proxy
+
+require (
+	github.com/chrj/smtpd v0.1.1
+	github.com/vharitonsky/iniflags v0.0.0-20180513140207-a33cd0b5f3de
+)

go.sum

@@ -0,0 +1,5 @@
+github.com/chrj/smtpd v0.1.1 h1:Jk9ZimOh4njDpMbDLPmdQX+x9AUYGrfE68EyjuQDPjk=
+github.com/chrj/smtpd v0.1.1/go.mod h1:jt4ydELuZmqhn9hn3YpEPV1dY00aOB+Q1nWXnBDFKeY=
+github.com/eaigner/dkim v0.0.0-20150301120808-6fe4a7ee9cfb/go.mod h1:FSCIHbrqk7D01Mj8y/jW+NS1uoCerr+ad+IckTHTFf4=
+github.com/vharitonsky/iniflags v0.0.0-20180513140207-a33cd0b5f3de h1:fkw+7JkxF3U1GzQoX9h69Wvtvxajo5Rbzy6+YMMzPIg=
+github.com/vharitonsky/iniflags v0.0.0-20180513140207-a33cd0b5f3de/go.mod h1:irMhzlTz8+fVFj6CH2AN2i+WI5S6wWFtK3MBCIxIpyI=

main.go

@@ -0,0 +1,45 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"net/smtp"
+
+	"github.com/chrj/smtpd"
+	"github.com/vharitonsky/iniflags"
+)
+
+var (
+	hostName   = flag.String("hostname", "localhost.localdomain", "Server hostname")
+	welcomeMsg = flag.String("welcome_msg", "", "Welcome message for SMTP session")
+	localHost  = flag.String("local_host", "localhost", "Address to listen for incoming SMTP")
+	localPort  = flag.Int("local_port", 25, "Port to listen")
+	remoteHost = flag.String("remote_host", "smtp.gmail.com", "Outgoing SMTP host")
+	remotePort = flag.Int("remote_port", 587, "Outgoing SMTP port")
+	remoteUser = flag.String("remote_user", "", "Username for authentication on outgoing SMTP server")
+	remotePass = flag.String("remote_pass", "", "Password for authentication on outgoing SMTP server")
+)
+
+func handler(peer smtpd.Peer, env smtpd.Envelope) error {
+
+	return smtp.SendMail(
+		fmt.Sprintf("%s:%d", *remoteHost, *remotePort),
+		smtp.PlainAuth("", *remoteUser, *remotePass, *remoteHost),
+		env.Sender,
+		env.Recipients,
+		env.Data,
+	)
+}
+
+func main() {
+
+	iniflags.Parse()
+
+	server := &smtpd.Server{
+		Hostname:	*hostName,
+		WelcomeMessage: *welcomeMsg,
+		Handler:        handler,
+	}
+
+	server.ListenAndServe(fmt.Sprintf("%s:%d", *localHost, *localPort))
+}

smtp-proxy.ini

@@ -0,0 +1,12 @@
+; smtp-proxy configuration
+
+;hostname = "localhost.localdomain"
+;welcome_msg = "<hostname> ESMTP ready."
+
+;local_host = 127.0.0.1
+;local_port = 25
+
+;remote_host = smtp.gmail.com
+;remote_port = 587
+;remote_user =
+;remote_pass =